answering information about your height and build and such will help, and you will soon enough be able to learn if a bike is even worth looking at from a rough glance at the picture. If the bike is too big or small, you will know to just pass it up and be patient, depending on hyow populated your CL is. I went through this process last spring and found the "Classic and Vintage Bicycles: What's it Worth? Appraisals and Inquiries" forum to be supremely helpful. If you can do some rough google search on a model before hand to figure out if the price is anywhere near right, then ask about it there, you will find a lot of help. I had people eventually talking to me about bikes they had in my size (Someone had a good bike in KC for me, but I didn't have the time or budget to drive across state at the time).
To be honest, the forum was a godsend, as a couple of St. Louis folks (where I live) pointed out some bikes to me. In the end, Tugadude had bought an 80's lower-end Bianchi off of CL and decided it was too small for him, and thought of me. I have to give him huge credit for his good deed. He PM'd me, offered to sell me the bike, met me halfway (geographically, not figuratively) because we live on opposite ends of the city, and sold me the bike for what he had picked it up for ($80-mind you he had already dedicated some of his time to shining it up a little and making sure everything was in working order) If I weren't a broke college student, I would've thrown in a little more just because he was so cool about it.
Anyways, point is, yes there will usually be people here who can help you, for someone new to the whole thing, this place can be an excellent resource, and finally, make sure you hit of the C&V appraisals section.